How do I stop my 10&12 diving into the ruck

My10&12 have a tendency to dive into the Ruck leaving a huge hole that my oppose score through. I have tried lowering my DefSpeed on the players and tried various Def Spacing but nothing seems to help. Can someone tell me how to keep the 10&12 stay in position? Many Thanks.
Look at both Attack and Defence Spacings and play with them until you get it right. Will also depend on your opposition spacings so you may have to adjust In-Game.
Thanks trying that now. It seems to be improving.
Cool and good luck.